Size determining mechanism for automatic machines



SIZ'E DETERMINING MECHANISM FOR AUTOMATIC MACHINES H. L. BLOOD Dec. 10,1935.

Filed Feb. 23, 1953 3 Sheets-Sheet l gwuentoz Harold. LiBxood fibto mugDec. 10, 1935. H. L. BLOOD 2,023,662

SIZE DETERMINING MECHANISM FOR AUTOMATIC MACHINES Filed Feb. 23, 1 53 sSheets-Shet 2 grwm H cnold 14.310001 a Ho mou Dec. 10, 1935. H. L. BLOODSIZE DETERMINING MECHANISM FOR AUTOMATIC MACHINES Filed Feb. 23, 1953nqets sheet 5 80 :lWC'H M 79 Z Harold L. Blood Patented Dec. 10, 1935SIZE DETERDIINING MECHANISM FOR AUTOMATIC MACHINES Harold L. Blood,Worcester, Mass, assignor to The Heald Machine Company, Worcester, Mass,a corporation of Massachusetts Application February 23, 1933, Serial No.658,028

19 Claims. (01. 51-165) In prior constructions'of automatic machinesmade in order thatsuccessive workpieces shall 10 of this character, thesize of the workpiece, beall be reduced to the same desired size. 1 ingoperated upon is'determined either by a gage The principal object of thepresent invention is mechanism of the type shown in the McDonough toprovide a novel arran'gementfor determining Reissue Patent No. 16,141,issued August 11, 1925, the size of a workpiece, which incorporates the1 a later construction of the same type being shown advantages of theabovedescribed constructions, 15

in the Kempton 8i Gallimore Patent No. 1,731,719, without incorporatingany of the disadvantagesissued October 15, 1929, or by the movement ofthe thereof. According to the present invention, the crossfeeclmechanism which causes the cutting size of the workpiece'isautomatically determined tool to cut progressively deeper and deeperinto by utilizing variations in thepotential of an elec the surface ofthe workpiece,- as shown in the trica-l circuit to controlthe-grindingoperations, 20

Guild Patent No. 1,682,672, granted August 28, such variationsofpotential resulting from'either 1928. removal of material from theworkpiece, or the" In the McDonough and Kempton & Gallimore appr a f agrinding wheel to a predetermined grinding machine constructions, thegage memp a In carrying u v t o the use 15 her is reciprocated relativeto the workpiece, and of sizing gages that fi the w p the the grindingoperation is interrupted when the utilization of the actual flow ofcurrent through workpiece is ground to such a size that the gage theworkpiece is avoided, the invention utilizing may enter the boretherein. While a. gaging instead small variations of voltage in anelectromechanism of the above indicated character is re p siv vi re infrom onta t wi h 0 entirely satisfactory in operation, it has beeneither the workpiece the inding Wheel, all

The present invention relates to automatic machines for the reduction ofworkpieces to a predetermined size, and although in certain of itsaspects it is applicable to various types of automatic machines, itsparticular utility, as will hereinafter appear, is in connection withmachines for treating, as by a cutting operation, the internal surfacesof sleeves, gears, bushings and like articles.

found that the continued hammering action of a gage against the end ofsuccessive workpieces before a given workpiece reaches the predeterminedsize, in addition to the wear on a gage as'it enters within the bore ofthe workpiece, will impair the accuracy of the gage, necessitatinginspection and replacement thereof in order to procure successiveworkpieces which are reduced consistently'to a predetermined size.

In a grinding machine construction of the type disclosed in the Guildpatent, the size of the workpieces is controlled by the movement of thecrossfeed mechanism whichoperates'to terminate the-grinding operationwhen the cutting surface of thegrinding wheel reaches a predeterminedvertical plane during the crossfeed movement.-

The locationof this plane; is determined by a dressing tool whichoperates during each grind-' tential obtained from theganparatus of Fig;2

to cause said wheel, during successive grinding operations, to move intothe above-noted predetermined vertical plane before the grindingoperation is terminated. Although machines of this construction are alsoentirely satisfactory 5 in operation, the inequalities inherent ingrinding wheels and the necessarily involved construction and operationof the-machine are such-that 1 frequent inspections and adjustments mustbe" as will hereinafter appear from the following detailed descriptiontaken in connection with the accompanying drawings, in which:-- I Fig. 1is a view in front elevation of an internal grinding machine embodyingthe invention. Fig. 2 is a fragmentary plan view of a portion of theparts of Fig. 1, on an enlarged scale.

Fig. 3 is a view in front elevation, showing a portion of the parts ofFig. 2 in a different position. a

Fig. 4 is a plan view similar to Fig, 2, showing a modification of theinvention.

Fig. 5 is an enlarged transverse sectionalview along the line 5--5 ofFig. 4, looking in thedire'c tionof the arrows.

Fig. 6 is a wiring dia'gr'am illustrating automatic control of themachine through,v'ariationsofpo Fig. fLis a wiringdiagrarn'similar tFig.6, 111 trating the part s id'difierent positionsl ,7

is a ir e d e e i lvstret nsautoef matic control of the machinethroughvariations' of potential obtained'fronithe app r uses Fig. 9 is afragmentaryview, similar to "Fig showing a further modificationoftheinv"Fig. 10 is a wiring diagram illustrating automatic control of themachine through variations of potential obtained from the apparatus ofFig. 9.

Fig. 11 is a wiring diagram, similar to Fig. 10, illustrating the partsin different positions.

Like reference characters refer to like parts in the different figures.

Referring first to Fig. 1, the machine provides the usual reciprocatorytable I provided in an internal grinding machine; either the grindingwheel or the work to be ground may be carried on said table, thereciprocations of the latter operating in either case to produce arelative movement between said grinding wheel and workpiece. In theconstruction shown, the table I supports and carries a wheelhead 2, andthe work to be operated upon is held in a workhead 3, the latter beingcarried by a bridge 4 which spans the s lideways, not shown, provided bythe machine frame, for the back and forth movement of the table I. Agrinding wheel 5 is mounted on a spindle 6 journaled in the wheelhead 2and a workpiece a is mounted in a suitable workholding chuck or otherclamping device 'I journaled in the workhead.

The back and forth movement of the table I to cause the wheel 5 to makethe required traverse of the workpiece a. may be procured in any wellknown manner, as by the use of the fluid pressure controlling andreversing mechanism, forming the subject matter of the Heald 8: GuildPatent No. 1,582,468, granted April 27, 1926. Such mechanism formsnopart of the present invention; it is sufiicient to note that thedriving means employed procures the reversal of the table at each end ofits normal grinding stroke by the use of spaced adjustable dogs 8 and 9carried by the table I and adapted alternately to engage and to move areversing member ID. The latter during the grinding operation, when thegrinding wheel 5 is moving back and forth within the workpiece a issituated between said dogs 8 and 9 in position to be alternately struckby said dogs and, by its consequent movement, effects the reversals ofthe table I. The grinding wheel 5 is rotated at a high speed in anysuitable manner and the workholding member 1 is also rotated at asomewhat slower speed by a belt drive, as will hereinafter appear.

The wheel head 2 of the machine is mounted on a cross-slide II which isarranged to have a transverse movement on suitable ways, not shown,

on the reciprocatory table, movement of said cross-slide being procuredby rotation of a threaded crossfeed shaft I2, the latter engaging aninternally threaded member, n66 shown, which is secured in any suitableway to the cross-slide. The crossfeed shaft I2 is rotated in astep-bystep movement by mechanism of the type disclosed in the abovenoted Guild Patent No. 1,682,672 to procure a feeding movement of thegrinding wheel 5 to cause said wheel to cut progressively deeper anddeeper into the workpiece a; for the purpose of the present invention,it is sufficient to note that a ratchet wheel, not shown, is engaged bya pawl I3 which is actuated in response to the reciprocations of thecarriage I, thereby procuring rotation of said crossfeed shaft I2carrying the grinding wheel transversely against the surface of theworkpiece.

In the previous operation of grinding machines of the type shown anddescribed in the aforesaid Patent No. 1,682,672, the grinding operationis interrupted before the workpiece reaches prede termined finishedsize, the interruption occurring in response to the movement of thecrossfeed mechanism to procure separation of the grinding wheel from theworkpiece, in order that a dressing operation may be performed on thewheel. After the dressing operation has been performed on the wheel, thegrinding operation is resumed until the workpiece is ground to apredetermined finished size, whereupon the grinding operation is broughtto a close by a second separation of the grinding wheel from the work inresponse to the crossfeed mechanism. And since the present inventionalso contemplates both an initial separation of the grinding wheel fromthe workpiece for truing, followed by resumption of the grinding tocomplete the work, there is shown in Fig. 1 as an illustrativeembodiment of the invention, certain of the same wheel controllingmechanism described in the aforesaid Patent No. 1,682,672, to whichmechanism automatic control through variations of electrical potentialhas been applied.

As previously pointed out, in normal operation of the machine, back andforth movement is imparted to the table I by the cooperation of thespaced dogs 8 and 9 with the reversing member I0, and for the purpose ofautomatically interrupting the grinding operation on the workpiece andseparating the wheel for the dressing operation, the machine provides alever I4 pivotally mounted on a shaft I5, as shown in the broken awayportion of Fig. 1. The lever I4 has integral therewith a magneticarmature I6 disposed in operative relation with respect to the core ofan electromagnet II, the unbalanced weight of the lever I4 tending tomaintain the armature I 6 spaced from the end of the electromagnet coreas long as the electromagnet I'I remains in a deenergized condition.Upon energization of the electromagnet I1 in a manner hereinafterdescribed, attraction of the armature I6 imparts upward movement to thelever I4 and causes the latter to .lift a latch I8, assuming that thegrinding wheelconditions, the block I9 is held in spaced relation to thestationary block 20 by the latch I8, but when the lever I4 is elevatedas described above, the latch I8 releases the block I9 and subsequentright hand travel of the table I involves relative sliding movementbetween the table and the block I9, owing to the obstruction which thereversing member ID imposes against the left hand table dog 8. Continuedtravel of the table I finally brings the stationary block 20 up againstthe then slidable block I9, whereupon the dog 8 becomes immovablysupported for shifting the reversing member I 0 to procure reversal ofthe table. The above described sliding movement of the block I9 on thetable I, when released by the latch I8, results in an amplified righthand stroke of the table to withdraw the wheel 5 from the workpiece aand the disposal in the temporarily amplified path of movement of thewheel 5 of a dressing device 22, in the manner fully described in theabove noted Patent No. 1,682,672. P

block I9, and as the table moves to the left,

offers enough resistance to movement of the block IS with the table todetain the block until the latch I8 is restored to its normal positionin which it positively holds the block l9 separated from the block 20.On the above noted amplified right hand dressing stroke of the table I,in order to prevent a repetition of the dressing stroke, an arm 24mounted on the latch pivot 2| strikes a lug 25 of a switch member 26pivotally mounted above the lever I4, thereby turning the switch member26 into the position shown to break the circuit through theelectromagnet l1 and re lease the lever l4, as will be hereinafter morefully described. Upon the resumption of the grinding operation afterdressing of the wheel as described above, the normal back and forthmovement of the table continues until the work is reduced to apredetermined finished size, whereupon the grinding operation is broughtto a close by a second separation of the grinding wheel from the work inresponse to the electric potential control of the present invention. Forthe purpose of obtaining a final run out of the table I into theposition shown in Fig. 1, there is provided a second lever 2'! mountedon the same shaft l5 as the lever l4, the lever 21 having integraltherewith an armature 28 responsive to an electromagnet 29, as shown inFig. 6. Normally, the unbalanced weight of the lever 21 maintains thearmature 28 away from the core of the electromagnet 29 while the latteris in a deenergized condition, and such is the condition of affairsduring the grinding operation. Upon energization of the electromagnet 29in the manner hereinafter described, the lever 21 is raised to move itsupper end into the path of the left hand table dog 8, while the table isin its left hand position. Since the table dog 8 is pivotally mounted onits block l9, right hand movement of the table after elevation of thelever 21 results in lifting of the dog 8 so that it is carried clear ofthe reversing member l0. Therefore, the table I is not reversed butcontinues its movement to the right carrying the grinding wheel 5 out ofthe workpiece a, the table being brought to a full stop by any suitablemeans, such as is shown in the aforesaid Heald & Guild Patent No.1,582,468. The return of the table I to the working position from thefully withdrawn position of Fig. 1 is effected by the shifting of a handlever 38 operatively connected to the reversing member l0, and on theleft hand movement of the table an arm 3! also mounted on the pivot 2istrikes a second lug 32 on the movable switch member 26, thereby turningthe switch member in a position to disconnect the electromagnet 29 fromits source. This turning movement of the switch member 26 upon theinitiation of another grinding cycle restores the switch member to theposition shown in Fig. 6 in readiness for the energization, at theproper time in the grinding of the next workpiece,'of the electromagnetl1 controlling the wheel dressing operation.

The above described mechanism for mechanically controlling the movementsof the table I carrying the grinding wheel is more fully described inthe above mentioned Guild Patent No.

1,682,672, and therefore forms no part of the present invention per se;the present invention,

electrical circuit resulting from either removal of material from theworkpiece, or the approach of the grinding wheel to a predeterminedplane. In other words, the table'controlllng mechanism described abovewith reference to Fig. 1' is merely 5 an illustrative embodiment of themanner in which any one of the several forms of potential control, nextto be described, can be applied to a grinding machine of the charactershown.

As best shown in Figs. 2 and 3, one form of the 0 potential controlcontemplated by the present invention embodies the use of a gagingfinger 33, one end of which provides a head 34 mounted on a block 35 ofpiezo-electric material of such character that an electro-motive forcewill be generated therein, in response to twisting of the block. ARochelle salt crystal is a well known example of such material of whichthe block 35 may be composed, the base of the block 35 being insulatedat 36 from a bracket 31 carried by and movable with the lower portion ofthe table i.

As indicated in Fig. 2, the base 31a of the bracket 31 is laterallyadjustable on the table through the provision of slots 38 receiving thetable bolts 39, so that the free end of the gaging finger 33 may be setso as to cause an inset 33a, preferably a diamond or other hardmaterial, to engage the periphery of the unreduced workpiecesubstantially coincidentally with the engagement of the grinding wheel 5at the initiation of the grinding operation. As the finger 33 enters theworkpiece it, its initial engagement with the inner periphery thereofwill result in a turning moment being exerted on the finger in aclockwise direction about the axis of the crystal block 35. This turningmoment will result in actual twisting of the crystal block 35 with thegeneration of an electro-motive force across leads ll] extending fromthe base of the block and the head 34, respectively. Obviously, removalof material from 40 the workpiece a by the grinding wheel 5 fromsuccessive working strokes of the wheel will result in a decrease of theturning moment exerted on the gaging finger 33 as the internal diameterof the workpiece increases. Therefore, the potential generated withinthe crystal block 35 will vary with each cut of the wheel, and theinvention contemplates the utilization of such variations of the crystalblock potential to automatically control the grinding operation, as willnext be described.

Since the electro-motive force impressed across the leads 40 by twistingof the crystal 35 is relatively small and the range of variation ofpotential is limited, the invention provides means for amplifying theeffect of potential variations of the crystal block so as to bettercontrol the energization of the electromagnets I1; and .29 respectively.One means of readily amplifying the potential of the crystal block isthrough theuse of a grid glow tube designated by the reference character4| in Fig. 6. The glow tube 4| comprises a filament 42, plate 43 andgrid 44, with the filament 42 energized from a portion 45a of thesecondary winding of a transformer T, thees primary Winding 46 of whichis connected across a suitable source of alternating current indicatedat 41. One terminal of another portion 45b of the transformer secondaryis connected to the grid 44 through a resistor 48 so as to give the grid44 a negative bias with respect to the anode or filament 42 of the tube.The plate 43'is connected in series with the energizing coils 49 and 50of relays that are adapted to control energization of the electromagnetsl1 and 29 respectively, '5

in a manner hereinafter described, with one terminal of coil 5|)connected to one side of the primary winding 49. Therefore, with theconnections shown, the coils 49 and 59 will be energize-d when the glowtube 4| passes suflicient current, as determined by the characteristicsof the coils.

With the connections shown in Fig. 6, in the absence of any potentialacross the crystal block 35, that is to say with the crystal in anuntwisted condition, the negative bias of the grid 44 by the windingportion 45b is such as to effectively prevent the passage of current bythe tube 4 I. However, when the crystal block 35 is twisted, as a resultof the engagement of the finger 33 with the workpiece a, the lead 49from the crystal block 35 to the grid 44 gives the grid 44 a positivebias sufficient to overcome the basic negative bias and cause the glowtube 4| to pass enough current to energize the relay-coils 49 and 59.Obviously, the amount of current passed by the tube will depend upon thedegree of positive bias by the crystal block 35, which in turn will bedependent upon the degree of engagement of the finger 33 with theworkpiece to twist the crystal block. The

' amount of twisting is at a maximum at the beginning of the grindingoperation and decreases I progressively as the material is removed, andthe manner in which the resulting variations in the degree ofenergization of the relay coils 49 and 59 to first cause withdrawal ofthe wheel from the workpiece, for truing, and then the final run out ofthe wheel when the workpiece is reduced to finished size will now bedescribed.

To this end, one terminal of the electromagnet H is connected to themovable contact 5| under the control of the relay coil 49, the contact5| being biased in the direction of a stationary contact 52 by a spring.53. This stationary contact 52 is adapted to be connected to ground, asindicated at 54 by relatively movable contacts 55 and 56, the contact 55being mounted on the table so as to engage the stationary contact 55just as the finger 33 carried by the crystal block 35 enters or leavesthe workpiece a. The other terminal of electromagnet I7 is connected toa stationary contact 51 engaged by the movable switch member 25 in theposition shown in Fig. 6, the switch member 26 being in turn connectedto the supply generator 58 shown as being grounded at 54a; With thecircuit connections just described, it is obvious that the electromagnetI! will remain in a deenergized condition as long as'the glow tube 4|passes enough current to hold the movable contact'5l out of engagementwith the stationary contact 52 at the time when the finger 33 isengaging the workpiece, and the table controlled contacts 55 and 56 arein engagement, as,shown in Fig. 6.

The terminals of electromagnet 29 are similarly connected to the movablecontact 59 under the control of relay coil 50 and to a stationarycontact 65 adapted to be engaged by the pivoted switch member 26, whenthe latter is moved into the position shown in dotted lines in Fig; 7.The movable relay contact 59 is normally biased in the direction of astationary contac 6| by a spring 62, so that the circuit of theelectromagnet 29'is adapted to be completed through the table controlledcontacts 55 and 55 only when'the current passed by the glow tube 4| isreduced to a value in which the relay coil 59 no longer maintains itsmovable contact 59 out of engagement with the stationary contact 6| Aspreviously pointed out, each left hand movementof the grinding wheel 5into contact with the workpiece a is accompanied by entrance of thefinger 33 into the workpiece, and at the beginning of the grindingoperation with the diameter of the workpiece substantially unreduced asindicated in Fig. 6, the twisting of the crystal block 35 is at amaximum. Thereafter during the early stages of the grinding operation,the crystal block 35 is twisted each time the finger 33 enters theworkpiece to such an extent that the potential across its leads 40 ismore than sufficient to overcome the basic negative grid bias and causethe glow tube 4| to pass enough current to fully energize the relaycoils' 49 and 50 and hold the movable contacts 5| and 59 out ofengagement with thecorresponding stationary contacts 52 and 6|, as shownin Fig. 6. ment of the contacts 55 and 56, during this phase of thegrinding operation has no effect upon the electromagnets IT and 29.

As the grinding operation proceeds and the diameter of the workpiece aincreases, the amount of twisting of the crystal block 35 graduallydecreases, with a corresponding decrease in the amount of current passedby the glow tube 4|. Therefore, after a number of reciprocations of thegrinding wheel 5, sufficient to reduce the workpiece a to roughing size,the amount of twisting of the crystal block 35 will be reduced to suchan extent that not enough current will be passed by the tube 4| t5energize the relay coil 49 and hold the movable contact 5| away fromstationary contact 52 as the finger 3-3 is about to leave the workpieceon the right hand stroke of the wheelhead. Therefore, the movablecontact 5| will engage the stationary contact 52 at this moment, andsince as previously pointed out, the table contact 55 is then inengagement with the stationary contact 55, the electromagnet 'i will beenergized as indicated in Fig. '7, thereby raising the lever 4. Sincethe lever is raised by energization of the electromagnet after thegrinding wheel 5 has started on its right hand movement, the resultinglifting of the latch I8 releases the block I9 and renders the table dog8 ineffective to turn the reversing member ID until after the table hasrun out far enough to withdraw the grinding wheel 5 from the work fortruing by the dressing tool 22, as previously described. The circuit ofthe electromagnet I1 is broken as the grinding wheel 5 is withdrawn, dueto the engagement of the lug 25 on the movable switch member 26 by thearm 24, thereby disconnecting contact 51 from the generator 58, see Fig.1.

With the switch member 26 in engagement with the contact 69 leading tothe electromagnet 29, as indicated in dotted lines in Fig. 7, thecircuit of the electromagnet 29 is then in condition to be completedupon engagement of the movable contact 59 with the stationary contact 6I, as will next be described. Upon resumption of the grinding operationfollowing truing of the wheel 5 as just described, the re-entry of thefinger 33 into the workpiece a, then reduced to roughing size, isaccompanied by just enough twisting of the crystal block 35 to cause thetube 4| to pass sufiicient current to energize therelay coil 50,although not enough to energize coil 49 as previously described.Therefore, the relay coil 59 still holds its movable contact 59 out ofengagement with stationary contact 6! as the wheel enters the workpiecefor the final cut, or cuts. The finger 33 carried by the Therefore, theengagecrystal black 35 is so set that removal of additionaoeaeccsubstantially no contact between the finger 33 and the workpiece, sothat there is no appreciable l the left hand table dog BI Consequently,on the succeeding right hand movement of the table, the dog 8 clears thereversing member it and the right hand movement of the table continuesto the Cal extreme run-out position shown in Fig. 1, following which thecompleted workpiece is removed. Upon initiation of the grindingoperation upon a new workpiece, the left hand movement of the table fromthe run-out position causes the arm iii to engage the lug 32 on themovable switch member 26, thereby breaking the circuit through the'electroet 29, when the switch member moves from the dotted to the fullline position of Fig. 7 to reengage the contact El. This partiallyrestores the circuit of the electromagnet ll, and

the gaging finger 38 associated with the crystal bloclr 535 resumescontrol of the grinding cycle in the manner previously described, so asto autotically cause the tool to be withdrawn for tru= ing when thewo'rlr reaches predetermined roughing size and to cause the tool to befinally run out from the work when the predetermined 1i 1 size isreached.

In the automatic control of the grinding cycle just described,variations of voltage indirectly resulting from removal of material fromthe workpiece have been utilized, but as previously pointed out, theinvention also contemplates utilization oi the actual approach'oi theperiphery oi the grinding wheel to a predeteed plane by the cross feedmovement to obtain the desired variations of voltage values. In Figs.and 5, a crystal block 35' is shown carried by a holder that is mountedon a bracket (it by a resilient member The resilient'meniber be is shownas a leaf spring, with one end received in the bracket 65, so that themember 35 tends to maintain the holder dB in a substantially. horizontalposition. The crystal block 35 extends in the directian of the grindingwheel 5 and terminates in a head carrying a ieeler bl oi wear-resistantmaterial adapted to be engaged by the periphery of the grinding wheelwhen the latter has been fed a predetermined amount withrespect to theworkpiece c. The end or? the holder ltd opposite to the head (ll carriesa child (38' that-is adapted to limit movement of the right hand end ofthe holder inresponse to a horizontal thrust exerted on ithe oppositeend by reason oi engagement of the ieeler bl by the periphery of thegrinding wheel 6. The onnot position of the ieeler bl with respect tothe wheel 5 is adjustable through the provision of bolts cooperatingwith slots lb provided in the bracket h t, as shown in Fig. 1.

At the beginning of a cycle or grinding opera tions on a workpiece a, itis obvious from Fig; 5 that the holder bi extends substantiallyhorizontally with the end of the feeler bl spacedan appreciable'distancefrom the periphery of the grinding wheel 5. As the grinding proceeds,each operation of the cross feed mechanism brings the periphery of thegrinding wheel nearer the the workpiece has been reduced to roughingsize, the next succeeding cross feed of the wheel head will cause theperiphery of the wheel 5 to engage the feeler tl. When this occurs, asubstantially horizontal thrust is exerted on the holder such 5 as totend to move the head 66 away from the wheel 5, but the setting of thestud $8 is such that any shifting of the holder 53 is prevented, andthere results an axial compression of the, crystal block 35' sufilcientto generate anelectro- 1o motive force therein. Obviously, the voltagegenerated within the crystal block 35' will vary with the pressureexerted by the wheel 5, and the mam ner in which such voltage variationsmay be employed to control energization of the electromagnets ill and 2%will next be described.

Referring to Fig. 8, a lead do from the crystal block 35' is shown asconnected to the grid 44 of a glow tube ill that is adapted to beenergized from a source dl in exactly the same manner as 20 describedwith reference to Fig. 6. Furthermore, the relay coils it and 5tare'connected in series with the plate (it, as shown in Fig. 6, so thatthe flow of current through these coils is directly controlled by theoutput of the tube ii.

The electromagnets ill and 2d are connected to the stationary contactsbl and 6d under the control of the movable switch member 26 in themanner previously described with reference to Fig. 6-, while the otherterminals of the electro- 30 magnets are connected to movable contactsii and 62 under the control of the relay coils it :and 50, respectively.With the coils ld and 5d in a deenergized condition as shown in Fig. 8,

,the'niovable contacts ll and it are held against 35.

' grinding wheel isoperating with its periphery at an appreciabledistance from the end of the feeler til. Consequently, there being novoltage generated in the crystal block 35, the basic negative grid biasprevents the passage of current by the tube ll, and the coils iii andtill remain completely deenergized. During thisstage of the grindingcycle engagement between the table controlled contacts and has no efiecton the circuits of the electromagnets iii and 29, in view of the factthat the movable contacts ll and T12 are maintained out of engagementwith the cor responding "stationary contacts 52 and 69, as shown in Fig.8.

its the grinding proceeds and the diameter of the workpiece increases,the wheel 5 comes closer 9 and closer to the feeler bl, and the bracketbit is so set that when the workpiece has been re- .-duced to roughingsize, the feeler til is engaged by the wheel 5 and the crystal block 35'axially cause the tube ll to pass enough current to energize the coiltil, the coil 39 being'designed to pull up its armature carrying themovable contact member it on considerably less current than is requiredfor the coil 50 to pull up its armature. When the movable relay contactll engages its stationary contact 52, the resulting energization of theelectromagnet ll raises the lever I l4 and automatically causesseparation of the grinding wheel from the workpiece, for truing. in themanner previously described with reference to Fig. 7.

- Upon return of thegrinding wheel to theworkpiece for completion of thegrinding operation, it is evident that the'feeler 61 will be engaged bythe grinding wheel with a greater pressure than before, so thatsufficient voltage will be generated in. the crystal block 35' to causethe tube to pass enough current to energize the coil 50. That is to say,the coil 50 is so designed that when the periphery of the "grindingwheel reaches a vertical plane corresponding to the position it occupieswhen the workpiece has been reduced to predetermined finished size,compression of the crystal block 35' is such as to cause energization ofthe coil 50. The resulting engagement of the movable contact 12 with thestationary contact 8| serves to energize the electromagnet 29- and liftthe lever 21. When this occurs, the succeeding righ hand movement of thetable is continued until the tool reaches the full run-out positionshown in Fig. 1, following which the completed workpiece is removed.Upon initiation of the grinding operation upon a new workpiece, thecircuit through the electromagnet 29 is broken by the switch member 26,as previously described, thereby partially restoring the circuit of theelectromagnet I1, whereupon the feeler 61 associated with the crystalblock 35' resumes control of the grinding cycle.

Referring now to Figs. 9 and 10, there is illustrated a furthermodification of the invention, whereby variations in the voltageimpressed on the grid of a glow tube may be obtained in a mannerdifferent from that previously described with reference to Figs. 6 and8, for the purpose of automatically controlling the grinding cycle. InFig. 9, an arm 11 is shown as being yieldingly supported on a bracket 18by a resilient member 19, the arm 11 normally extending in asubstantially vertical direction. The bracket 18 is adjustably mountedon a portion of the machine base, a screw 80 serving to shift thebracket 18 and its arm 17 with respect to the axis of the grinding wheel5. The lower end of the arm 'II carries an inset Ila of wear resistantmaterial,

and feeding movement of the grinding wheel 5 with respect to theworkpiece a will cause the" periphery of the wheel to engage the inset"a. p and to shift the arm Tlon its flexible support I8 in such adirection as to swing the upper end of the arm away from an upwardextension 18a of the bracket 18.

With the grinding wheel 5 spaced from the lower end of the arm 11, as atthe beginning of the grinding cycle, the upper end of the arm 11 is inengagement with a contact 8.| adjustable within an insulating bushing8|a on the bracket extension 18a (while a flexible contact finger 82also can'ied by the arm 11 but insulated therefrom is in engagement witha contact 83 carried by the bracket extension 18a and insulatedtherefrom, as by a bushing 83a. With the parts in the position shown inFig. 9, the contact finger 82 is under a slight initial compression, sothat when the grinding wheel 5, due to its feeding movement, engages thearm: I1 as shown in Fig.

11, the end of the arm 11 will be disengaged from the upper contact 8|,while the contact finger 82 remains in engagement with the contact 83.The contact 83 is so adjusted with respect to the finger 82 that a veryslight further movement of the arm." from the position shown in Fig. 11

will cause the finger 82- to leave the contact 83. With the abovedescribed arrangement, it is apparent then that the arm 11 will leavethe contact 8| when the periphery of the grinding wheel 5 reaches apredetermined plane, and that the 5 contact finger 82 will leave thecontact 83 when the periphery of the wheel 5 reaches another planeparallel to but slightly removed from the first plane.

Referring now to Fig. 10, the plate 43' of a 10 grid glow tube 4| isconnected directly to one terminal of the electromagnet H, the otherterminal of the electromagnet I! being connected to one side of theprimary winding 46'-of a transformer T, so that the electromagnet I!will be is energized when the tube 4 I passes sufiicient current. Thefilament 42 of the tube 4| is energized from a portion 84 of thesecondary of transformer T, and with the parts in the position of Fig.10, a negative bias is maintained on the grid 20 44 by a secondarywinding portion 85 having one terminal thereof connected through theengaged arm Tl and contact 8|- to one end of the grid 44 through theusual resistor 48. The secondary winding of transformer T also providesa third portion 88, the function of which is to place a positive bias onthe grid 44 through an adjustable potentiometer connection at 86a, soset that normally the negative bias from winding 85, through the contact8|, is more than sufiicient to overcome the positive bias and preventthe tube 4| from passing any appreciable current. This condition ofaifairs is maintained during the first part of the grinding cycle and aslong as the arm 11 engages contact 8|. The electromagnet 29 controllingthe lever 21 has one terminal thereof connected to a plate 43" of asecond grid glow tube 4|", the other terminal of the electromagnet beingconnected to one side of the primary winding 48" of a second transformerT". The filament 42" of this tube 4|" is energized from a secondarywinding portion 81 in substantially the same manner as is the filament42' of tube 4| energized from winding 84. With the parts in the positionof Fig. 45 10,'the tube 4|" is prevented from passing any appreciablecurrent by reason of the fact that a negative bias is placed on the grid44" by means of a secondary winding portion 88 connected to one end ofthe grid 44" through the then closed contact finger 82 and contact 83.It is to be vnoted that one terminal of the negative bias winding 88 isconnected directly to thecontact. finger 82, and that the latter isinsulated from the, arm 'II, so that the circuits for controlling thenegative bias of grids 44' and 44" are mainthat the positive bias isless than the negative bias, and the tube 4 therefore passes no currentat the beginning of the grinding cycle. With the 7 parts arranged asdescribed with reference to Fig. 10, it is apparent that while theelectromagnets l1 and 29 are directly under the control of the glowtubes 4| and 4|", these tubes are both maintained in such a conditionthat they will'not pass sufflcient current to energize either theelectromagnet H or the electromagnet 29 during the first part of thegrinding cycle.

Referring now to Fig. 11, it is evident that when the grinding cycleproceeds to the point that the workpiece a has been reduced to roughingdiameter, the wheel 5 will engage the lower 76 iii) end of the arm Tl,whereupon shifting of the arm ii on its resilient supporting member 19-will cause the upper end thereof to leave the stationary contact at, asindicated. When this occurs, the basic negative bias on the grid M 'isimmediately removed, so that the positive bias from the secondarywinding portion 88 immediately becomes efiectiveon the grid M. The tubeil thereupon passes sumcient current to energize the electromagnet ii,the resulting lifting of the lever iii, as shown, autotically causingseparation of the wheel a from theworkpiece c for truing. The circuit ofthe electromagnet ii is broken as the grinding wheel is withdrawn, dueto the engagement of the lug it on the movable switch member 26 by thearm lid, see Fig. 1, thereby disengaging a'bridging contact at on theswitch member 23 from the spaced stationary contacts 92- in'the circuitof the electromagnet, as indicated in dotted lines in Fig. ll. Uponresumption of the grinding operation after truing, it is evident thatfurther removal oi material from the workpiece to bringit topredetermined finished diameter will cause the wheel 5 to further shiftthe arm ill from the position of Fig. 11, so asto separate the flexiblecontact finger 82 from the contact at. When this occurs, removal of thenegative bias from winding portion 88 on the grid dd" immediately causesthe tube M" to pass current, due to the positive bias impressed on thegrid M" by the secondary winding portion ta. This passage of current bythe tube it" is sumcient to energize the elcctromagnet 2t and cause thegrinding wheel ii to be moved to the finalrun-outposition of Fig. 1. Atthis time the circuit from the electromagnet 29 is maintained by abridging contact 93 on switch member 25, which bridging contact @8 is inengagement with stationary contacts dd when the switch member 25 is inthe dotted line position. Upon the initiation of the grinding operationupon a news workpiece, obviously the above described cycle of operationswill be repeated.

From the foregoing, it is apparent that by the present invention thereis provided a size determining mechanism of the above indicated type,characterized by the automatic control of the entire grinding cyclethrough variations of electrical potential resulting from either removalof material from the workpiece, or the approach of the grinding wheel toa predetermined plane. In other words, the control ofthe grinding cycleis obtained without the use of sizing gages that fit within theworkpiece, or without utilization of the actual now of current throughthe workpiece or the grinding wheel.

I. claim: T

i. In a mechanism or the class described, the combination with a cuttingtool, means for holding a workpiece, means to procure a cuttingoperation between said tool and workpiece by feeding movement of thetool relative to the'workpiece, and an electromagnet adapted to bringabout the separation of said tool from said workpiece, of a glow tubefor controlling the energization of said electromagnet, and meansdependent upon variations in the internal condition of anelectroresponsive material for automatically subjecting.

the grid of saidjsube to a voltage such as to cause it to pass enoughcurrent to energize said. magnet and cause separation of the tool fromthe workpiece when said workpiece reaches a predetermined diameter.

2. In mechanism of the class described, the combination with a cuttingtool, means for holdoperation in accordance inga workpiece, means toprocure a cutting operation between said tool and workpiece by feedingmovement of the tool relative to the workpiece, and an electromagnetadapted to bring about the separation of said tool from said workpiece,of a glow 'tube for energizing said electromagnet, said tube havinga'basic negative grid bias to restrict its passage of current, and meansdependent upon variations in the internal condition of anelectro-responsive material resulting from the removal of material fromsaid workpiece for creating a voltage sufllcient to overcome thenegative grid bias and cause said tube to pass 'suflicient current toenergize said electromagnet.

3. In mechanism of the class described, the

' combination with a cutting tool, means for holdmovement of the toolrelative to the workpiece,

and an electromagnet adapted to bring about the separation of said toolfrom said workpiece, of a glow tube for energizing said electromagnet,said glow tube having a basic negative grid bias to restrict its passageof current; and meansdependent upon variations in the internal conditionof an electro-responsive material resulting from the approach of saidtool to a predetermined plane for overcoming said negative grid bias andcausingsaid tube to pass sufilcient current to energize saidelectromagnct.

c. In a mechanism for performing a cutting operation on a workpiece by acutting tool, involving feeding movement of the tool relative to theworkpiece, an electrical circuit, piezoelectric material in said circuitand means for automatically' controlling the progress of the cuttingoperation in accordance with variations of the voltage generated in saidelectrical circuit by said piezoelectric material, as a result of suchfeeding movement between tool and workpiece.

5. In a mechanism for performing a cutting operation on a workpiece byreciprocatory movernent between the workpiece and a cutting tool,accompanied by feeding of the tool relative to the workpiece, anelectrical circuit, piezoelecsaid piezoelectric material when subjectedto variations of its internal condition resulting directly from suchreciprocatory movement.

6. In a mechanism for performing a cutting operation on a workpiece byreciprocatory movement between the workpiece and a cutting tool,accompanied ,by feeding of the tool relative to the workpiece, anelectrical circuit. piezoelectric material in said circuit and means forautomatically controlling the progress of the cutting operation inaccordance with variations of the voltage generated in said electricalcircuit by said piezoelectric material as a result of the application offorce tending to deform the material due to rcci'procatory movement ofthe cutting tool.

7. In a mechanism for performing a cutting operation on a workpiece byreciprocatory movement between the workpiece and a cutting tool,accompanied by feeding of the tool relative to the workpiece, anelectrical circuit, a piezoelectrio crystal in said circuit and meansfor automatically controlling the progress of the cutting withvariations of'the voltage generated in said electrical circuit by thedeformation of said piezo-electric crystal resulting from directengagement of said crystal with the workpiece.

8. In a machine of the class described, the

combination with a cutting tool, means for hold- 5 ing a workpiece, andmeans to procure the removal of material from the workpiece by a cuttingoperation resulting from relative feeding movement between said tool andworkpiece, of

an electrical circuit, piezoelectric material in said 10 circuit andmeans for'automatically controlling the cutting operation of the machinein response to variations in the voltage of said electrical circuit,with said piezoelectric material being sub- .iect to variations of itsinternal condition result- 15 ing from the removal of material from saidworkpiece.

9. In a machine of the class described, the combination with a cuttingtool, means for holding a workpiece, and means to procure the removal of2 material from the workpiece by a cutting operation resulting fromrelative feeding movement between said tool and workpiece, of anelectrical circuit, piezo electric material in said circuit and meansfor automatically interrupting the cutting 25 operation when theworkpiece reaches a predetermined size in response to a voltagegenerated in said electrical control circuit with said piezo electricmaterial being subject to variations in its internal condition resultingfrom the removal of 30 material from said workpiece.

10. In a machine of the class described, the combination with a cuttingtool, means for holding a workpiece, and means to procure the removal ofmaterial from the workpiece by a cutj 35 ting operation resulting fromrelative feeding movement between said tool and workpiece, of anelectric circuit, piezo electric material in said circuit and means forautomatically interrupting the cutting operation in response to thegenera: 4 tion of a voltage in said electrical control circuit, withsaid piezo electric material being subject to variations in its'internal condition by the approach of the cutting toolto a predeterminedplane due to its feeding movement toward said 4.3 workpiece.

11. In a machine of the class described, the combination with a cuttingtool, meansfor holding a workpiece, and means to procure the removal ofmaterial from the workpiece by a cutto ting operation resulting fromrelative feeding movement between said tool and workpiece, of anelectric circuit, piezo electric material in said circuit ancimeans forautomatically interrupting the cutting operation in resp'onseto thegenera- 05 tion of a voltage in said electrical control circuit, withsaidpiezo electric material being subject to variations in,its internalcondition due to reduction in the size' of the workpiece.

12. In a machine of the class described, the

60 combination with a cutting tool, means for holding a workpiece, andmeans to procure the removal of material from the workpiece by a cuttingoperation resulting from. relative feeding movement between said tooland workpiece, of a 05 control circuit for said machine, and anelectroresponsive material in said circuit adapted to enerate a voltagein said circuit due to deforma tion of the material by engagement withthe cutting tool as the latterapproaches a predeter- 7o mined plane inits feeding movement with respect to the workpiece.

13. In a machine of the class described, the combination with a cuttingtool, means for holding a workpiece, and .means to procure the re- 75'moval of material from the workpiece by a cutting operation resultingfrom relative feeding movementbetween said tool and workpiece, of acontrol circuit for said machine and an electroresponsive material insaid circuit adapted to generate a voltage in the circuit as a result of5 deformation of the material due to its engagement with the workpiece.

14. In a machine of the class described, the combination with a cuttingtool, means for holding a workpiece, and means to procure the re- 10moval of material from the workpiece by a cutting operation resultingfrom relative feeding movement between said tool and workpiece, or agaging member supported by a block of piezoelectric crystal and anelectrical circuit for controlling the operation of the machine, saidcircuit including said crystal and being responsive to voltagesgenerated through the deformation of said crystal as a result of therelative feeding movement between said tool and workpiece. 2o

15. In a machine of the class described, the combination with a cuttingtool, means for holding a workpiece and means to procure the removal ofmaterial from the workpiece by, a cutting operation resulting fromrelative feeding movement between said tool and workpiece, of anelectrical control circuit, piezo electric material in said circuitsubject to variations in its internal condition due to relative feedingmovement between said tool and workpiece, which variations are reflectedin said control circuit,

and means under the supervision of said circuit for automaticallyinterrupting the cutting operation when the workpiece reaches apredetermined size. I 16. In a machine of the class described, thecombination with a cutting tool, means for holding a workpiece and meansto procure the removal of material from the workpiece by a cuttingoperation resulting from relative feeding movement between said tool andworkpiece, of an electrical control circuit, piezo electric material insaid circuit subject to variations in its internal condition by theapproach of the cutting tool to a predetermined plane due to its feedingmovement toward said workpiece, which variations are reflected in saidcontrol circuit, and means under the supervision of said circuit forautomatically interrupting the cutting operation when the workpiecereaches a predetermined size. 17. In a machine of the class described,the combination with a cutting tool, means for holding a workpiece andmeans to procurethe removal of material from the workpiece by a cuttingoperation resulting from relative feeding movement between said tool andworkpiece, of an electrical control circuit, piezo electric material insaid circuit subject to variations in its internal condition due toreducton in size of the workpiece, which variations are reflected insaid control circuit, and means under the supervision of said circuitfor automatically interrupting the cutting operation when the workpiecereaches a predetermined size.

18. In a grinding machine, the combination with a workholder, a grindingwheel, and means to procure a grinding cycle on a workpiece carried bysaid holder, of an electric circuit, piezo electric material in saidcircuit subject to variations in its internal condition due to relativefeeding movement between the workpiece and the grinding wheel, and meansunder the influence of said circuit to automatically control theprogress of the grinding cycle, said cycle being characterized bytemporary separation of the wheel from the workpiece for truing, whenthe workpiece is reduced to roughing size, and final separation of thewheel from the workpiece when'the latter reaches a predeterminedfinished size.

19. In a. grinding machine, the combination with a workholder, agrinding wheel, and means to procure a grinding cycle on a workpiececarried by said holder, of an electric circuit, piezo electric materialin said circuit subject to deformation due to relative feeding movementbetween the workpiece and the grinding wheel, and means responsive tovariations in the voltage of said circuit resulting from deformation ofsaid piez'o electric material to automatically control the progress ofthe grinding cycle, one voltage value causing temporary separation ofthe wheel from the workpiece for truing, when the workpiece is reducedto roughing size, and a second voltage value causing final separation ofthe wheel from the workpiece when the latter is reduced to predeterminedfinished size.

HAROLD L. BLOOD.

